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Objectives DDescribe how stress forces affect rock. DDescribe the types of faults, why faults form and where they occur. DDescribe how movement along faults changes Earth’s surface. DDescribe how stress forces affect rock. DDescribe the types of faults, why faults form and where they occur. DDescribe how movement along faults changes Earth’s surface.

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Have you experienced an earthquake? DDescribe the event DWhere were you at the time? DHow did you know that it was an earthquake? DWhat happens to the building and objects around you? DHow did you feel during and after? DDescribe the event DWhere were you at the time? DHow did you know that it was an earthquake? DWhat happens to the building and objects around you? DHow did you feel during and after?

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Discover Activity D4. Repeat Steps 1 and 2. This time, however, keep bending the ends of the popsicle stick toward each other. What happens to the wood? DWhat do you think might eventually happen as the forces of plate movement bend the crust? D4. Repeat Steps 1 and 2. This time, however, keep bending the ends of the popsicle stick toward each other. What happens to the wood? DWhat do you think might eventually happen as the forces of plate movement bend the crust?

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Discover Activity Questions DWhen you bent the popsicle stick the first time and held it in an arch shape, what was happening? DAnswer: Energy - the “push” applied by the hands - was being transferred to the stick and stored in it. DWhat would have happened if you had suddenly let go of one end of the bent stick, and why? DWhen you bent the popsicle stick the first time and held it in an arch shape, what was happening? DAnswer: Energy - the “push” applied by the hands - was being transferred to the stick and stored in it. DWhat would have happened if you had suddenly let go of one end of the bent stick, and why?

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Discover Activity Questions DAnswer: the stick would have sprung back to its original shape because the stored energy was quickly released. DWhere did this stored energy go? DAnswer: It was released as energy in the form of heat. DAnswer: the stick would have sprung back to its original shape because the stored energy was quickly released. DWhere did this stored energy go? DAnswer: It was released as energy in the form of heat.

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Earth’s Crust in Motion DStress in the crust Earthquake - the shaking and trembling that results from the movement of rock beneath Earth’s surface. Stress - the movement of Earth’s plates creates powerful forces that squeeze or pull the rock in the crust. DStress in the crust Earthquake - the shaking and trembling that results from the movement of rock beneath Earth’s surface. Stress - the movement of Earth’s plates creates powerful forces that squeeze or pull the rock in the crust.

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Types of Stress These types work over millions of years to change the shape and volume of rock. Some rocks can become brittle and snap, others bend slowly like road tar softened by the sun. DShearing - this stress pushes a mass of rock in two opposite directions. Causes rock to break, slip apart, or to change its shape. DTension - pulls on the crust, stretching rock that that it becomes thinner in the middle. These types work over millions of years to change the shape and volume of rock. Some rocks can become brittle and snap, others bend slowly like road tar softened by the sun. DShearing - this stress pushes a mass of rock in two opposite directions. Causes rock to break, slip apart, or to change its shape. DTension - pulls on the crust, stretching rock that that it becomes thinner in the middle.

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Types of Stresses DCompression - squeezes rock until it folds or breaks. DDeformation is any change in the volume or shape of Earth’s crust. DCompression - squeezes rock until it folds or breaks. DDeformation is any change in the volume or shape of Earth’s crust.

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Try This Activity - It’s a Stretch (p. 145) DYou can model the stresses that create faults. DMaterials - playdough D1. Demonstrate the three types of stresses by: DA. pushing the ends toward the middle DB. pull the ends apart. DC. push half of the putty one way and the other half in the opposite direction. DYou can model the stresses that create faults. DMaterials - playdough D1. Demonstrate the three types of stresses by: DA. pushing the ends toward the middle DB. pull the ends apart. DC. push half of the putty one way and the other half in the opposite direction.

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Kinds of Faults DP Read first paragraph. DFault - a break in Earth’s crust where slabs of crust slip past each other. They usually occur along plate boundaries where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks. DP Read first paragraph. DFault - a break in Earth’s crust where slabs of crust slip past each other. They usually occur along plate boundaries where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks.

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Strike-slip fault DStrike-slip fault - shearing causes these faults. Rocks on either side of the fault slip past each other sideways with little up-or-down motion. They also form transform boundaries. DExample - San Andreas fault DStrike-slip fault - shearing causes these faults. Rocks on either side of the fault slip past each other sideways with little up-or-down motion. They also form transform boundaries. DExample - San Andreas fault

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Strike-Slip Fault DP Irregular, shadowed line running up the middle of the photograph. Look at the road at the bottom of the photograph. DIf a strong earthquake occurred, what do you think would happen to the road where it crosses the fault? Why? DAnswer: The road would be bent out of alignment or broken because the two slabs of crust on opposite sides of the fault are moving in different directions. DP Irregular, shadowed line running up the middle of the photograph. Look at the road at the bottom of the photograph. DIf a strong earthquake occurred, what do you think would happen to the road where it crosses the fault? Why? DAnswer: The road would be bent out of alignment or broken because the two slabs of crust on opposite sides of the fault are moving in different directions.

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Strike-Slip Fault DWhat other things might be deformed or broken at a fault? DAnswer: Fences, rivers and streams, bridges, driveways, straight rows of trees or crops, etc. DWhat other things might be deformed or broken at a fault? DAnswer: Fences, rivers and streams, bridges, driveways, straight rows of trees or crops, etc.

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Normal fault DThe fault is at an angle, so one block of rock lies above the fault while the other block lies below the fault.

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Normal Fault DThe half of the fault that lies above is called the hanging wall. DThe half of the fault that lies below is called the footwall. DFacts & Figures - p. 146 TE DThe half of the fault that lies above is called the hanging wall. DThe half of the fault that lies below is called the footwall. DFacts & Figures - p. 146 TE

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Exit Slip DMake a simple sketch of each type of fault without referring to the diagrams on the pages, add arrows to schow the bock movements, and label each sketch thewith name of the type of fault it shows. Put in journal if you have one.

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Friction Along Faults DWhat is friction? DWhat are some examples of low friction that you’ve experienced? DLow friction - ice or polished floor DWhat are some examples of times when people use high friction to their advantage? DHigh friction - sanding, rubber-soled sneakers, filing fingernails DWhat is friction? DWhat are some examples of low friction that you’ve experienced? DLow friction - ice or polished floor DWhat are some examples of times when people use high friction to their advantage? DHigh friction - sanding, rubber-soled sneakers, filing fingernails

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Friction Along Faults DFriction is the force that opposes the motion of one surface as it moves across another surface. DRead p. 148 DSan Andreas Fault - Friction is high. DFriction is the force that opposes the motion of one surface as it moves across another surface. DRead p. 148 DSan Andreas Fault - Friction is high.

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Mountain Building DOver millions of years, fault movement can change a flat plain into a towering mountain range. DMountains Formed by Faulting When normal faults uplift a block of rock, a fault-block mountain forms. DTeton Range near Wyoming and Idaho was formed this way. (Slide Show) DOver millions of years, fault movement can change a flat plain into a towering mountain range. DMountains Formed by Faulting When normal faults uplift a block of rock, a fault-block mountain forms. DTeton Range near Wyoming and Idaho was formed this way. (Slide Show)

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Mountains Formed by Folding DHave you ever skidded on a rug that wrinkled up as your feet pushed it across the floor? DFolds - bends in rock that form when compression shortens and thickens part of Earth’s crust. DHave you ever skidded on a rug that wrinkled up as your feet pushed it across the floor? DFolds - bends in rock that form when compression shortens and thickens part of Earth’s crust.

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Himalayas in Asia - caused by folds

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Alps in Europe - caused by folds

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Anticlines and Synclines DAnticline - A fold in rock that bends upward into an arch. DSyncline -A fold in rock that bends downward in the middle to form a bowl.